This application addresses Studies to improve access and utilization of HIV counseling and testing for HIV/AIDS and AIDS-related co-infections such as hepatitis C virus (HCV), other sexually transmitted infections (STIs) that are part of PA-07-307 Drug Abuse Aspects of HIV/AIDS. The only rapid tests that are approved for use in the US currently are for HIV infection. Tests for other conditions such as hepatitis C (HCV) and syphilis are in use in other countries. In response to an Opportunity that the CDC published in the Federal Register, there are now candidate rapid test kits for HCV and syphilis available for experimental use in the US. This project will conduct a two-part study to assess the experimental rapid tests for accuracy and acceptability. In part 1, the Center for Behavioral Research and Services (CBRS) will ship serum from an existing serum bank to CDC where the serum samples will be tested with the rapid test kits for HCV, syphilis, and HIV. The results will be sent back to CBRS where the previous standard laboratory test results will be unblinded and the CDC experimental test results will be assessed for sensitivity and specificity as compared to the standard test results. In part 2, different combinations of rapid and standard tests will be offered to participants in a four-arm trial to assess which tests are accepted by the participants. Only a minority of clients at CBRS who have been offered the rapid test for HIV have accepted it. Those who chose rapid HIV tests were more likely to be male, educated, gay, young and White. They were less likely to be Black, or injection drug users. The proposed study has the potential to have a significant impact upon screening for HIV, syphilis, and HCV. Rapid tests have the potential to increase the receipt of test results, particularly among groups that are less likely to return for their results using traditional testing. The data from the proposed study will contribute to FDA-approval for the experimental screening tests. The candidate tests are designed for Point of Care (either oral fluid and/or whole blood), and thus will require real-time testing after they have been validated on the serum samples, so the trial will be able to evaluate both the accuracy of the tests in settings of intended use and their acceptability to potential clients in real-world situations.